May 26, 192 1] 



NATURE 



405 



The fourth annual general meeting of the Society 

 of Glass Technology was held at University College, 

 London, on April 20, when Dr. Morris W. Travers 

 was elected president in succession to Mr. S. N. 

 Jenkinson. The new president delivered an address 

 on the importance of quantitative investigation in 

 dealing with technical glass problems. The speaker 

 directed attention to the fact that the late Lord 

 Moulton, who was to have presided at the society's 

 dinner that evening, had brought about a great im- 

 provement in the efficiency of explosives factories by 

 applying quantitative investigation to the processes 

 conducted in them. The energy balance-sheet of a 

 factory was as important as its financial balance- 

 sheet, and the efficiency of a furnace, for instance, 

 should be accurately known so that a full account 

 could be given of all heat which entered it. This 

 principle was illustrated by application to several 

 furnace problems. There was also a wide field for 

 investigations bearing on the nature of glass, and 

 recent work had shown that glass in the solid condi- 

 tion resembled the elastic gels rather than the liquids. 

 A paper on automatic glass-feeding devices was com- 

 municated by Messrs. G. Dowse and E. Meigh, and 

 the society's third annual dinner followed. During 



the course of the evening the president referred to 

 the proposed legislation affecting the industry, and 

 maintained that the total prohibition of the importa- 

 tion of all chemical glassware except under licence 

 was essential to that branch of the industry. Elec- 

 tric lamp bulbs should also have been included in 

 the Bill. Assistance would be necessary if the manu- 

 facture of these articles were to be continued in thijS 

 country. 



Messrs. G. E. Stechert and Co., 151 West 25th 

 Street, New York (London : 2 Sta? Yard, Carey 

 Street, W.C.2), have sent us a copy of their cata- 

 logue (New Series, xl.) of second-hand books relating 

 to natural history. It contains some hundreds of 

 titles, and is classified as follows : — General Natural 

 Science ; Agriculture, Forestry, Farming ; Botany ; 

 Zoology ; Ornithology ; Ichthyology ; Entomology ; 

 Gardening ; and Supplement. The prices asked (in 

 American dollars) appear to be very moderate. 



An interesting little catalogue (No. 414) of nearly 

 four hundred works (books and engravings) on the 

 topography of Kent and Sussex has just been issued 

 by Mr. F, Edwards, 83 High Street, Mar>lebone, W.i. 

 It will doubtless appeal to residents in the two 

 counties named and to manv others. 



Our Astronomical Column. 



Comets. — It appears that Dubiago's comet was dis- 

 covered by him at Kasan on April 24, and observed 

 -at Pulkovo a few days later. It has now been ob- 

 served in England by Dr. Steavenson, whose observa- 

 tions enable the orbit to be improved. This has 

 already been done approximated with the following 

 result : — 



T 1921 May 7-177 G.M.T., w 100° 13', Q 65° 58', 

 2 22° 20', log g 0-0481. 



Ephemeris for Greenwich Midnight. 



May 28 

 June 



Its total lig-ht is probably equal to a 9th magni- 

 tude star ; it should be readify visible in an ordinary 

 telescope in the absence of the'moon. 



The errors of the ephemeris of comet Pons-Win- 

 necke have become so large that it is well to give the 

 revised orbit lately received from Prof. Crawford and 

 Miss Levy, with the ephemeris, for. Greenwich mid- 

 nigrht, deduced from it. 



T 1921 June 12-95 G.M.T., to 170° 34', i7, 97° 51', 

 i 18° 50', log^ q 0-01703, e 0-6779, period (assumed) 

 5-8 years. 



R.A. Decl. Log r Log A 



h. m. s. o , 



May 27 19 35 27 43 16 N. 0-0272 9-2698 



31 20 16 47 39 36 0-0230 92226 



June 4 21 o 39 33 "52 0-0198 9- 18 18 



8 21 44 21 26 4 0-0178 9-1537 



12 22 24 42 16 37 00170 9-1446 



16 23 o 20 6 50 N. 0-0175 * 9-1572 



20 23 31 5 2 14 S. 0-0192 9-1881 



24 23 56 42 9 55 S. 0-0221 9-2295 



After this the comet will travel south rapidly; it should 

 NO. 2691, VOL. 107] 



be observable in the southern hemisphere until 

 September. 



Theory of Jupiter's Satellites. — Prof. Sampson's 

 tables of Jupiter's satellites have been in use in the 

 national ephemerides for several years, but the theory 

 on which they were based has only just appeared in 

 print, being vol. Ixiii. of Memoirs of the Royal Astro- 

 nomical Society. The author commences with a 

 review of the work of Laplace, Delambre, Damoiseau, 

 and Souillart; he explains that the discordances that 

 still exist between the tables and observation are due 

 to the fact that in deducing the fundamental elements 

 with the aid of the older theories it was assumed 

 that only the leading terms of these would be involved. 

 It was discovered (too late to alter the tables) that 

 some secondary terms in the older theories were so 

 seriously wrong that the tables are sensibly affected. 

 One such error may affect the time of an 'eclipse of 

 Satellite IV. by 140s. 



The elements at the present day were derived chieflv 

 from the Harvard photometric observations of eclipses. 

 These permit of the deduction of an exceedinglv 

 accurate value of the equatorial semi-diameter of 

 Jupiter; the mean of the Harvard and Durham dis- 

 cussions is 18-927". 



The adopted value of Jupiter's mass is 1/1047-35, 

 but it is noted that a discussion of recent measures 

 and photographs in conjunction with the theory leads 

 to the value 1/ 1047-0. It would, however, be rash to 

 alter the accepted value, which rests largely on the 

 perturbations of minor planets and the comet Pons- 

 Winnecke. 



One advantage of the delav in publishing the 

 theory is that it has enabled a list to be given of the 

 errata and omissions that have been detected. One 

 such was found soon after the tables were printed, 

 and a supplementary page was issued. 



Mr. Innes directed attention to two omitted .terms ; 

 one, due to the effect of the sun on Satellite IV., has 

 a coefficient of 7-6". The other is a long-period term ; 

 period for III. 26^ years, coefficient about 6*. The 

 values for IV. are not verv different. 



